Reptiles are true terrestrial animals that breed on land. They live in countries with hot climates, and as they move away from the tropics, their number noticeably decreases. The limiting factor for their spread is temperature, since these cold-blooded animals are active only in warm weather, in cold and hot weather they burrow into holes, hide in shelters or fall into torpor.

In biocenoses, the number of reptiles is small and therefore their role is little noticeable, especially since they are not always active.

Reptiles feed on animal food: lizards - insects, mollusks, amphibians; snakes eat many rodents and insects, but at the same time pose a danger to domestic animals and humans. Herbivores land turtles cause damage to gardens and vegetable gardens; aquatic ones feed on fish and invertebrates.

People use the meat of many reptiles for food (snakes, turtles, large lizards). Crocodiles, turtles and snakes are exterminated for their skin and horny shell, and therefore the numbers of these ancient animals have greatly decreased. There are crocodile breeding farms in the USA and Cuba.

The Red Book of the USSR includes 35 species of reptiles.

There are about 6,300 known species of reptiles, which are much more widespread around the globe than amphibians. Reptiles live mainly on land. Warm and moderately humid areas are most favorable for them; many species live in deserts and semi-deserts, but only very few penetrate into high latitudes.

Reptiles (Reptilia) are the first terrestrial vertebrates, but there are some species that live in water. These are secondary aquatic reptiles, i.e. their ancestors switched from a terrestrial lifestyle to an aquatic one. Among reptiles, poisonous snakes are of medical interest.

Reptiles, together with birds and mammals, form a superclass of higher vertebrates - amniotes. All amniotes are true terrestrial vertebrates. Thanks to the embryonic membranes that have appeared, their development is not associated with water, and as a result of the progressive development of the lungs, adult forms can live on land in any conditions.

The eggs of reptiles are large, rich in yolk and protein, covered with a dense parchment-like shell, and develop on land or in the mother’s oviducts. There is no aquatic larva. A young animal hatched from an egg differs from adults only in size.

Class characteristics

Reptiles are included in the main trunk of vertebrate evolution, since they are the ancestors of birds and mammals. Reptiles appeared at the end Carboniferous period approximately 200 million years BC, when the climate became dry and in some places even hot. This created favorable conditions for the development of reptiles, which turned out to be more adapted to living on land than amphibians.

A number of traits contributed to the advantage of reptiles in competition with amphibians and their biological progress. These include:

• the membrane around the embryo (including the amnion) and a strong shell (shell) around the egg, protecting it from drying out and damage, which made it possible to reproduce and develop on land;
• further development of the five-fingered limb;
• improvement of the structure of the circulatory system;
• progressive development of the respiratory system;
• appearance of the cerebral cortex.

The development of horny scales on the surface of the body, protecting against adverse influences, was also important. environment, primarily from the drying effect of air.

Reptile body divided into head, neck, torso, tail and limbs (absent in snakes). Dry skin is covered with horny scales and scutes.

Skeleton. The spinal column is divided into five sections: cervical, thoracic, lumbar, sacral and caudal. The skull is bony, there is one occipital condyle. In the cervical spine there is an atlas and epistropheus, due to which the head of reptiles is very mobile. The limbs end in 5 fingers with claws.

Musculature. Much better developed than amphibians.

Digestive system. The mouth leads into the oral cavity, equipped with a tongue and teeth, but the teeth are still primitive, of the same type, and serve only to capture and hold prey. The digestive tract consists of the esophagus, stomach and intestines. At the border of the large and small intestines the rudiment of the cecum is located. The intestine ends in the cloaca. Developed digestive glands(pancreas and liver).

Respiratory system. In reptiles, the respiratory tract is differentiated. The long trachea branches into two bronchi. The bronchi enter the lungs, which look like cellular thin-walled sacs with a large number of internal partitions. The increase in the respiratory surface of the lungs in reptiles is associated with the lack of cutaneous respiration. Breathing is only pulmonary. The breathing mechanism is of the suction type (breathing occurs by changing the volume of the chest), more advanced than that of amphibians. Conducting airways (larynx, trachea, bronchi) are developed.

Excretory system. It is represented by secondary kidneys and ureters flowing into the cloaca. The bladder also opens into it.

Circulatory system. There are two circles of blood circulation, but they are not completely separated from each other, due to which the blood is partially mixed. The heart is three-chambered (crocodiles have a four-chambered heart), but consists of two atria and one ventricle; the ventricle is divided by an incomplete septum. The systemic and pulmonary circulations are not completely separated, but the venous and arterial flows are more clearly separated, so the reptile body is supplied with more oxygenated blood. The separation of flows occurs due to the septum at the moment of heart contraction. When the ventricle contracts, its incomplete septum, attached to the abdominal wall, reaches the dorsal wall and separates the right and left halves. The right half of the ventricle is venous; the pulmonary artery departs from it, the left aortic arch begins above the septum, carrying mixed blood: the left, part of the ventricle is arterial: the right aortic arch originates from it. Converging under the spine, they unite into the unpaired dorsal aorta.

The right atrium receives venous blood from all organs of the body, and the left atrium receives arterial blood from the lungs. From the left half of the ventricle, arterial blood enters the vessels of the brain and the anterior part of the body, from the right half, venous blood blood is flowing into the pulmonary artery and further into the lungs. The trunk region receives mixed blood from both halves of the ventricle.

Endocrine system. Reptiles have all the endocrine glands typical of higher vertebrates: pituitary gland, adrenal glands, thyroid gland, etc.

Nervous system . The brain of reptiles is different from the brain of amphibians great development hemispheres. The medulla oblongata forms a sharp bend, characteristic of all amniotes. The parietal organ in some reptiles functions as a third eye. The rudiment of the cerebral cortex appears for the first time. There are 12 pairs of cranial nerves leaving the brain.

Sense organs are more complex. The lens in the eyes can not only get mixed up, but also change its curvature. In lizards, the eyelids are movable; in snakes, the transparent eyelids are fused. In the olfactory organs, part of the nasopharyngeal passage is divided into olfactory and respiratory sections. The internal nostrils open closer to the throat, so reptiles can breathe freely when they have food in their mouths.

Reproduction. Reptiles are dioecious. Sexual dimorphism is pronounced. Gonads are paired. Like all amniotes, reptiles are characterized by internal insemination. Some of them are oviparous, others are ovoviviparous (that is, a baby immediately emerges from the laid egg). Body temperature is not constant and depends on the ambient temperature.

Taxonomy. Modern reptiles are divided into four subclasses:

1. proto-lizards (Prosauria). Protolizards are represented by a single species - the hatteria (Sphenodon punctatus), which is one of the most primitive reptiles. The tuateria lives on the islands of New Zealand.
2. scaly (Squamata). This is the only one regarding large group reptiles (about 4000 species). The scaly ones include
   • lizards. Most lizard species are found in the tropics. This order includes agamas, poisonous teeth - poisonous lizards, monitor lizards, true lizards, etc. Lizards are characterized by well-developed five-fingered limbs, movable eyelids and eardrums [show] .

     The structure and reproduction of a lizard

     Fast lizard. The body, 15-20 cm long, is covered on the outside with dry skin with horny scales, which form quadrangular scutes on the abdomen. The hard cover interferes with the uniform growth of the animal; the change of the horny cover occurs through molting. In this case, the animal sheds the upper horny layer of scales and forms a new one. The lizard molts four to five times during the summer. At the ends of the fingers, the horny cover forms claws. The lizard lives mainly in dry, sunny places in steppes, sparse forests, bushes, gardens, on hillsides, railway and highway embankments. Lizards live in pairs in burrows, where they spend the winter. They feed on insects, spiders, mollusks, worms, and eat many crop pests.

     In May-June, the female lays from 6 to 16 eggs in a shallow hole or burrow. The eggs are covered with a soft, fibrous, leathery shell that protects them from drying out. Eggs have a lot of yolk, the white shell is poorly developed. All development of the embryo occurs in the egg; after 50-60 days the young lizard hatches.

     In our latitudes, lizards are often found: quick, viviparous and green. All of them belong to the family of true lizards of the order Squamate. The agama family belongs to the same order (steppe agama and round-headed agama - inhabitants of deserts and semi-deserts of Kazakhstan and Central Asia). Scaly ones also include chameleons that live in the forests of Africa, Madagascar, and India; one species lives in southern Spain.

   • chameleons
   • snakes [show]

     The structure of snakes

     Snakes also belong to the order Scaly. These are legless reptiles (some retain only rudiments of the pelvis and hind limbs), adapted to crawling on their belly. Their neck is not pronounced, the body is divided into head, torso and tail. The spine, which contains up to 400 vertebrae, is highly flexible thanks to additional articulations. It is not divided into departments; almost every vertebra bears a pair of ribs. In this case, the chest is not closed; the sternum of the belt and limbs are atrophied. Only some snakes have preserved a rudimentary pelvis.

     The bones of the facial part of the skull are connected movably, the right and left parts of the lower jaw are connected by very stretchable elastic ligaments, just as the lower jaw is suspended from the skull by stretchable ligaments. Therefore, snakes can swallow large prey, even larger than the snake's head. Many snakes have two sharp, thin, poisonous teeth curved back, sitting on the upper jaws; they serve to bite, capture prey and push it into the esophagus. Poisonous snakes have a longitudinal groove or duct in the tooth through which the venom flows into the wound when bitten. The poison is produced in the modified salivary glands.

     Some snakes have developed special thermal sense organs - thermoreceptors and thermolocators, which allows them to find warm-blooded animals in the dark and in burrows. The tympanic cavity and membrane are atrophied. Eyes without lids, hidden under transparent skin. The snake's skin becomes keratinized on the surface and is periodically shed, i.e., molting occurs.

     Previously, up to 20-30% of victims died from their bites. Thanks to the use of special therapeutic serums, mortality decreased to 1-2%.

3. crocodiles (Crocodilia) are the most highly organized reptiles. They are adapted to an aquatic lifestyle, and therefore have swimming membranes between the toes, valves that close the ears and nostrils, and a velum that closes the pharynx. Crocodiles live in fresh waters and come to land to sleep and lay eggs.
4. turtles (Chelonia). Turtles are covered above and below with a dense shell with horny scutes. Their chest is motionless, so their limbs take part in the act of breathing. When they are drawn in, air leaves the lungs, and when pulled out, it enters again. Several species of turtles live in the USSR. Some species, including the Turkestan tortoise, are eaten.

The meaning of reptiles

Antisnake serums are currently used for medicinal purposes. The process of making them is as follows: horses are successively injected with small but ever-increasing doses of snake venom. Once the horse is sufficiently well immunized, blood is taken from it and a therapeutic serum is prepared. Recently, snake venom has been used in medicinal purposes. It is used for various bleedings as a hemostatic agent. It turned out that in hemophilia it can increase blood clotting. A drug made from snake venom - vipratox - reduces pain from rheumatism and neuralgia. To obtain snake venom and to study the biology of snakes, they are kept in special nurseries. Several serpentariums operate in Central Asia.

Over 2 thousand species of snakes are non-venomous, many of them feed on harmful rodents and bring significant benefits to the national economy. Non-venomous snakes include snakes, copperheads, snakes, and steppe boas. Water snakes sometimes eat juvenile fish in pond farms.

The meat, eggs and shells of turtles are very valuable and are exported. The meat of monitor lizards, snakes, and some crocodiles is used as food. Valuable skin of crocodiles and monitor lizards is used to make haberdashery and other products. Crocodile breeding farms have been created in Cuba, the USA and other countries.

Reptiles- typical terrestrial animals and their main method of movement is crawling, reptiles on the ground. Key Features The structures and biology of reptiles helped their ancestors leave the water and spread widely across the land. These features primarily include internal fertilization And egg laying, rich in nutrients and covered with a dense protective shell, which facilitates their development on land.

The body of reptiles has protective formations in the form scales, covering them with a continuous cover. The skin is always dry, evaporation through it is impossible, so they can live in dry places. Reptiles breathe exclusively with the help of their lungs, which, compared to the lungs of amphibians, have a more complex structure. Intensive lung breathing became possible thanks to the appearance of a new skeletal section in reptiles - chest. The chest is formed by a number of ribs connected on the dorsal side to the spine, and on the abdominal side to the sternum. The ribs, thanks to special muscles, are mobile and contribute to the expansion of the chest and lungs during inhalation and their collapse at the moment of exhalation.

Changes in the structure of the respiratory system are closely related to changes in blood circulation. Most reptiles have a three-chambered heart and two circuits of blood circulation (as do amphibians). However, the structure of the reptile heart is more complex. In its ventricle there is a septum, which at the moment of contraction of the heart almost completely divides it into the right (venous) and left (arterial) halves.

This structure of the heart and the location of the main vessels, different from that of amphibians, more strongly delineates the venous and arterial flows, therefore, the body of reptiles is supplied with blood that is more saturated with oxygen. The main vessels of the systemic and pulmonary circulation are typical of all terrestrial vertebrates. The main difference between the pulmonary circulation of amphibians and reptiles is that in reptiles the cutaneous arteries and veins have disappeared and the pulmonary circulation includes only pulmonary vessels.

About 8,000 are known today existing species reptiles that live on all continents except Antarctica. Modern reptiles are divided into orders: protolizards, scaly, crocodiles And turtles.

Reproduction of reptiles

Fertilization in terrestrial reptiles internal: the male injects sperm into the female’s cloaca; they penetrate the egg cells, where fertilization occurs. The female's body develops eggs, which she lays on land (buries in a hole). The outside of the egg is covered with a dense shell. The egg contains a reserve nutrients, due to which the development of the embryo occurs. The eggs do not produce larvae, as in fish and amphibians, but individuals capable of independent life.

First Lizard Squad

TO proto-lizards refers to "living fossil" - tuateria- the only species that has survived to this day only on small islands near New Zealand. This is a sedentary animal, leading a predominantly nocturnal lifestyle and appearance lizard-like. Hatteria in its structure has features that are similar to reptiles and amphibians: the vertebral bodies are biconcave, with a chord preserved between them.

Otrad scaly

Typical representative scaly - quick lizard. Its appearance indicates that it is a terrestrial animal: the five-fingered limbs do not have swimming membranes, the fingers are armed with claws; the legs are short, and therefore the body, when moving, seems to crawl along the ground, every now and then coming into contact with it - reptiles (hence the name).

Lizards

Although the lizard's legs are short, it can run quickly, quickly escaping from its pursuers into its burrow or climbing a tree. This was the reason for its name - quick. The lizard's head is connected to the cylindrical body using the neck. The neck is poorly developed, but will still give the lizard's head some mobility. Unlike a frog, a lizard can turn its head without turning its whole body. Like all land animals, it has through nostrils, and its eyes have eyelids.

Behind each eye, in a small depression, is the eardrum, connected to the middle and inner ear. From time to time, the lizard sticks out of its mouth a long, thin tongue forked at the end - an organ of touch and taste.

The lizard's body, covered with scales, rests on two pairs of legs. The humerus and femur bones are parallel to the surface of the earth, causing the body to sag and drag along the ground. TO thoracic vertebrae the ribs are attached to form the rib cage, protecting the heart and lungs from damage.

The digestive, excretory and nervous systems of the lizard are basically similar to the corresponding systems of amphibians.

Respiratory organs - lungs. Their walls have a cellular structure, which significantly increases their surface area. The lizard does not have skin respiration.

The lizard's brain is better developed than that of amphibians. Although it has the same five sections, the forebrain hemispheres are larger in size, and the cerebellum and medulla oblongata are much more massive.

The sand lizard is distributed very widely from the Black Sea to Arkhangelsk region, from the Baltic Sea to Transbaikalia. In the north, it gives way to a viviparous lizard similar to it, but more adapted to the cold climate. IN southern regions lives a lot different types lizards Lizards live in burrows, which in summer weather they leave in the morning and evening, but no further than 10-20 m from the burrow.

They feed on insects, slugs, and in the south - locusts, caterpillars of butterflies and beetles. Within a day, one lizard can destroy up to 70 insects and plant pests. Therefore, lizards deserve protection as very useful animals.

The lizard's body temperature is not constant (the animal is active only in warm time year), it drops sharply even if a cloud approaches the sun. With a longer drop in temperature, the lizard loses mobility and stops eating. During the winter it hibernates; can tolerate freezing and cooling of the body down to -5°, -7°C, while all the life processes of the animal slow down significantly. Gradual warming returns the lizard to active life.

In addition to the sand lizard and viviparous lizard, there are many other species of lizards. Common in Ukraine and the Caucasus large green lizard: in desert areas - agama lizards with a long flexible and unbreakable tail.

Predatory lizard gray monitor lizard, living in the deserts of Central Asia. Its length is up to 60 cm. The monitor lizard eats arthropods, rodents, eggs of turtles and birds. Most large specimens monitor lizards discovered by herpetologists (the science that studies reptiles) on the island of Komolo reach 36 cm. In the northern regions, a legless lizard is common - spindle.

Chameleons

Chameleons in appearance they resemble medium-sized lizards, with a helmet-shaped outgrowth on the head and a laterally compressed body. This is a highly specialized animal, adapted to an arboreal lifestyle. His fingers are fused together like pincers, with which he tightly grasps the branches of trees. The long and prehensile tail is also used for climbing. The chameleon has a very unique eye structure. The movements of the left and right eyes are not coordinated and independent of each other, which provides some advantages when catching insects. Interesting feature Chameleon's ability to change skin color is a protective device. Chameleons are common in India, Madagascar, Africa, Asia Minor and southern Spain.

Snakes

In addition to lizards, the order Squamate includes snakes. Unlike chameleons, snakes are adapted to crawling on their stomachs and swimming. Due to wave-like movements, the legs gradually completely lost their role as organs of locomotion; only some snakes retained their rudiments (a boa constrictor). Snakes move by bending their legless body. Adaptation to crawling was manifested in the structure internal organs snakes, some of them completely disappeared. Snakes have no bladder and only one lung.

Snakes see poorly. Their eyelids are fused, transparent and cover their eyes like a watch glass.

Among the snakes there are non-venomous and poisonous species. The largest non-venomous snake is boa- lives in the tropics. There are boas up to 10 m long. They attack birds and mammals, strangling their prey by squeezing it with their body, and then swallowing it whole. Large boas living in tropical forests, are also dangerous for humans.

Widespread of non-venomous snakes snakes. The common snake is easily distinguished from poisonous snakes by two orange crescent spots on the head and round pupils of the eyes. It lives near rivers, lakes, ponds, feeding on frogs, and sometimes small fish, swallowing them alive.

Poisonous snakes include viper, cobra, or spectacled snake, rattlesnake and etc.

Viper easily recognized by the long zigzag dark stripe running along the back. In the upper jaw of the viper there are two poisonous tooth with channels inside. Through these tubules, the poisonous liquid secreted by the salivary glands of the snake enters the wound of the victim, and the victim, for example a mouse or small bird, dies.

By destroying huge numbers of mice and locusts, vipers benefit humans. However, their bites can cause long-term illness and even death in animals and even humans. The venom of such snakes as asian cobra, American rattlesnake.

Wounds formed when a person is bitten by a snake look like two red dots. Painful swelling quickly occurs around them, gradually spreading throughout the body. A person develops drowsiness, cold sweat, nausea, delirium, severe cases death comes.

When biting a person poisonous snake urgent first aid measures must be taken, remove excess poison near the wound with blotting paper, cotton wool or a clean cloth, if possible, disinfect the bite site with a manganese solution, strictly protect the wound from contamination, give the victim strong tea or coffee, and ensure rest. Then take him to the hospital as quickly as possible for immediate administration of anti-snake serum. Where there are poisonous snakes, you should not walk barefoot. Care must be taken when picking berries, protecting your hands from snake bites.

Otrad crocodiles

Crocodiles- these are the largest and most highly organized predatory reptiles, adapted to an aquatic lifestyle, living in tropical countries. Nile crocodile Spends most of its life in water, where it swims beautifully, using a strong, laterally compressed tail, as well as hind limbs that have swimming membranes. The crocodile's eyes and nostrils are elevated, so it only needs to raise its head out of the water a little and it can already see what is happening above the water, and also breathe atmospheric air.

On land, crocodiles are slow to maneuver and, when in danger, rush into the water. They quickly drag their prey into the water. These are various animals that the crocodile lies in wait at watering places. It can also attack humans. Crocodiles hunt mainly at night. During the day they often lie motionless in groups on the shallows.

Turtle squad

Turtles differ from other reptiles in their well-developed, durable shell. It is formed from bone plates, covered on the outside with horny substance, and consists of two shields: the upper convex and the lower flat. These shields are connected to each other from the sides, and there are large gaps in front and behind the joints. The head and forelimbs are exposed from the front, and the hind limbs from the back. Almost all aquatic turtles are predators, while land turtles are herbivores.

Turtles typically lay hard-shelled eggs on land. Turtles grow slowly, but are among the long-livers (up to 150 years). There are giant turtles (soup turtle up to 1 m long, weight - 450 kg, swamp turtle - up to 2 m and up to 400 kg). They are objects of fishing.

Meat, fat, eggs are used for food, and a variety of horn products are made from the shell. We have one species of turtles - marsh turtle, lives up to 30 years. During the winter it hibernates.

Reptiles reproduce on land. Fertilization in them is internal. Reptiles reproduce in three ways:

- oviparity, that is, the female lays eggs;

- oviparity when the embryo develops in an egg in the reproductive tract of the mother's body, it feeds on the nutrients of the egg, from which it hatches soon after it is laid. (Remember that vertebrate animals are also characterized by oviparity and ovoviviparity.);

- viviparity, in which the embryo develops in the mother’s body and receives nutrients from it. Through this method of reproduction, the female gives birth to babies. This type of reproduction is characteristic of only some sea snakes.

The temperature of incubation of reptile eggs determines the sex of the offspring that will be born. In crocodiles and turtles, when incubated at temperatures above +30 C, only females are born, and if the temperature is below this indicator, only males are born.

In May-June, the female sand lizard lays 6 to 16 large eggs containing a supply of nutrients - the yolk - in a shallow hole or burrow. It is necessary so that the embryo has the opportunity to develop over a long period of time and be born in the form of a small lizard. Lizard eggs are always covered with a soft, leathery shell (the shell of turtle and crocodiles eggs is hard). The scarlet shell prevents damage and drying out of the egg. However, in an environment that is too dry, the eggs can dry out, so sufficient moisture is a necessary condition for the normal development of the embryo.

The development of embryos in eggs continues for two months. At the end of summer, young lizards 4-5 cm long emerge from them, which immediately begin independent life, feeding on the smallest insects. In October, the young hide for the winter. The lizard grows throughout its life, its length can be about 25 centimeters. In the second or third year of life, having a length of up to 10 cm, it becomes sexually mature.

The life expectancy of reptiles is the longest among all vertebrates. Lizards live up to 20 years, snakes - up to 60, and crocodiles and turtles can live up to 100. The elephant turtle lives longer - more than 150 years.

Reptiles are terrestrial animals. The transition to a completely land-based lifestyle took place thanks to the following adaptation features: dense body cover, which prevents moisture loss, and the presence of eggs with protective shells, as a result of which reptiles are able to reproduce on land.

Terms and concepts: class Reptiles, or Reptiles; horny scales, scutes, rings, autotomy, thoracic, tulubo-lumbar, caudal spine, rib cage, intercostal muscles, pelvic kidneys, ureters, urethra, larynx, bronchi, Jacobson's organ, viviparity, yolk, scarlet membrane.

Check yourself. 1. What are the features external structure and individual development distinguish reptiles from amphibians? 2. The structure of the integument of reptiles? 3. How are the skeletons of a lizard and a frog different? 4. Name the fundamental differences in the excretory system of a lizard and a frog and explain what caused them. 5. What sense organs do they have? highest value for lizard orientation? 6. What are oviparity, ovoviviparity and viviparity?

How do you think? Why do lizards become more active in hot sunny weather, but become lethargic during cold weather?

The class Reptiles (reptiles) includes about 9,000 living species, which are divided into four orders: Squamate, Crocodiles, Turtles, Beaked. The latter is represented by only one relict species - hatteria. Scaly animals include lizards (including chameleons) and snakes.

The sand lizard is often found in middle lane Russia

General characteristics of reptiles

Reptiles are considered the first true terrestrial animals, since they are not associated in their development with aquatic environment. Even if they live in water (aquatic turtles, crocodiles), they breathe with their lungs and come to land to reproduce.

Reptiles are distributed over land much more widely than amphibians and occupy more diverse ecological niches. However, due to their cold-blooded nature, they predominate in warm climates. However, they can live in dry places.

Reptiles appeared from stegocephalians (an extinct group of amphibians) at the end of the Carboniferous period of the Paleozoic era. Turtles appeared earlier, and snakes appeared later than everyone else.

The heyday of reptiles occurred in Mesozoic era. At this time, various dinosaurs lived on Earth. Among them were not only terrestrial and aquatic species, but also flying ones. Dinosaurs went extinct at the end of the Cretaceous period.

Unlike amphibians, reptiles

improved head mobility due to a larger number of cervical vertebrae and a different principle of their connection to the skull;

the skin is covered with horny scales that protect the body from drying out;

breathing is only pulmonary; the chest is formed, which provides a more advanced breathing mechanism;

although the heart remains three-chambered, the venous and arterial blood flows are better separated than in amphibians;

pelvic kidneys appear as excretory organs (and not the trunk ones as in amphibians); such kidneys retain water in the body better;

the cerebellum is larger than that of amphibians; the volume of the forebrain is increased; the rudiment of the cerebral cortex appears;

internal fertilization; reptiles reproduce on land mainly by laying eggs (some are viviparous or ovoviviparous);

embryonic membranes (amnion and allantois) appear.

Reptile skin

The skin of reptiles consists of a multilayer epidermis and connective tissue dermis. The upper layers of the epidermis become keratinized, forming scales and scutes. The main purpose of scales is to protect the body from water loss. In general, the skin is thicker than that of amphibians.

The scales of reptiles are not homologous to the scales of fish. Horny scales are formed by the epidermis, i.e., they are of ectodermal origin. In fish, scales are formed by the dermis, that is, they are of mesodermal origin.

Unlike amphibians, there are no mucous glands in the skin of reptiles, which is why their skin is dry. There are only a few scent glands.

In turtles, a bony shell is formed on the surface of the body (top and bottom).

Claws appear on the fingers.

Since keratinized skin inhibits growth, reptiles are characterized by molting. At the same time, the old integument moves away from the body.

The skin of reptiles grows tightly together with the body, without forming lymphatic sacs, like in amphibians.

Reptile skeleton

In comparison with amphibians, the spine of reptiles is no longer divided into four, but five sections, since the trunk section is divided into thoracic and lumbar.

In lizards, the cervical region consists of eight vertebrae (in various types there are from 7 to 10 of them). The first cervical vertebra (atlas) is like a ring. The odontoid process of the second cervical vertebra (epistrophy) enters it. As a result, the first vertebra can rotate relatively freely around the process of the second vertebra. This gives greater head mobility. In addition, the first cervical vertebra is connected to the skull by one mouse, and not two like in amphibians.

All thoracic and lumbar vertebrae have ribs. In lizards, the ribs of the first five vertebrae are attached to the sternum by cartilage. The chest is formed. The ribs of the posterior thoracic and lumbar vertebrae are not connected to the sternum. However, snakes do not have a sternum and therefore do not form a rib cage. This structure is associated with the characteristics of their movement.

The sacral spine in reptiles consists of two vertebrae (and not one, as in amphibians). The iliac bones of the pelvic girdle are attached to them.

In turtles, the vertebrae of the body are fused with the dorsal shield of the shell.

The position of the limbs relative to the body is on the sides. Snakes and legless lizards have reduced limbs.

Digestive system of reptiles

The digestive system of reptiles is similar to that of amphibians.

The oral cavity contains a movable, muscular tongue, which in many species is forked at the end. Reptiles are able to throw it far.

In herbivorous species, a cecum appears. However, most are predators. For example, lizards eat insects.

The salivary glands contain enzymes.

Respiratory system of reptiles

Reptiles breathe only with their lungs, since due to keratinization the skin cannot take part in respiration.

The lungs are improved, their walls form numerous partitions. This structure increases the inner surface of the lungs. The trachea is long, at the end it is divided into two bronchi. In reptiles, the bronchi in the lungs do not branch.

Snakes have only one lung (the right one, and the left one is reduced).

The mechanism of inhalation and exhalation in reptiles is fundamentally different from that of amphibians. Inhalation occurs when the chest expands due to stretching of the intercostal and abdominal muscles. At the same time, air is sucked into the lungs. When you exhale, the muscles contract and air is pushed out of the lungs.

Circulatory system of reptiles

The heart of the vast majority of reptiles remains three-chambered (two atria, one ventricle), and arterial and venous blood are still partially mixed. But compared to amphibians, in reptiles the venous and arterial blood flows are better separated, and, therefore, the blood mixes less. There is an incomplete septum in the ventricle of the heart.

Reptiles (like amphibians and fish) remain cold-blooded animals.

In crocodiles, the ventricle of the heart has a complete septum, and thus two ventricles are formed (its heart becomes four-chambered). However, blood can still mix through the aortic arch.

Three vessels independently depart from the ventricle of the heart of reptiles:

It departs from the right (venous) part of the ventricle common trunk pulmonary arteries, which further divides into two pulmonary arteries leading to the lungs, where the blood is enriched with oxygen and returns through the pulmonary veins to the left atrium.

Two aortic arches extend from the left (arterial) part of the ventricle. One aortic arch begins to the left (however called right aortic arch, as it bends to the right) and carries almost pure arterial blood. From the right aortic arch originate the carotid arteries leading to the head, as well as the vessels supplying the girdle of the forelimbs with blood. Thus, these parts of the body are supplied with almost pure arterial blood.

The second aortic arch extends not so much from the left side of the ventricle, but from its middle, where the blood is mixed. This arch is located to the right of the right aortic arch, but is called left aortic arch, since at the exit it bends to the left. Both arches of the aorta (right and left) on the dorsal side are connected into a single dorsal aorta, the branches of which supply mixed blood to the organs of the body. Venous blood flowing from the organs of the body enters the right atrium.

Excretory system of reptiles

In reptiles, in the process embryonic development the trunk kidneys are replaced by the pelvic ones. The pelvic kidneys have long nephron tubules. Their cells are differentiated. Reabsorption of water occurs in the tubules (up to 95%).

The main excretion product of reptiles is uric acid. It is almost insoluble in water, so the urine is mushy.

The ureters extend from the kidneys and empty into the bladder, which opens into the cloaca. In crocodiles and snakes, the bladder is underdeveloped.

Nervous system and sensory organs of reptiles

The brain of reptiles is being improved. In the forebrain, the cerebral cortex appears from the gray medulla.

In a number of species, the diencephalon forms the parietal organ (third eye), which is capable of perceiving light.

The cerebellum in reptiles is better developed than in amphibians. This is due to the more diverse motor activity of reptiles.

Conditioned reflexes are difficult to develop. The basis of behavior is instincts (complexes of unconditioned reflexes).

The eyes are equipped with eyelids. There is a third eyelid - the nictitating membrane. Snakes have transparent eyelids that grow together.

A number of snakes have pits at the front end of their heads that receive thermal radiation. They are good at determining the difference between the temperatures of surrounding objects.

The organ of hearing forms the inner and middle ear.

The sense of smell is well developed. There is a special organ in the oral cavity that distinguishes odors. Therefore, many reptiles stick out their tongue, forked at the end, taking air samples.

Reproduction and development of reptiles

All reptiles are characterized by internal fertilization.

Most lay eggs in the ground. There is a so-called ovoviviparity, when the eggs are retained in the female’s genital tract, and when they emerge from them, the young hatch immediately. U sea ​​snakes true viviparity is observed, with the embryos developing a placenta similar to the placenta of mammals.

Development is direct, a young animal appears, similar in structure to the adult (but with an underdeveloped reproductive system). This is due to the presence of a large supply of nutrients in the yolk of the egg.

In the eggs of reptiles, two embryonic membranes are formed, which are not present in the eggs of amphibians. This amnion And allantois. The embryo is surrounded by an amnion filled with amniotic fluid. The allantois is formed as an outgrowth of the posterior end of the intestine of the embryo and performs the functions of the bladder and respiratory organ. The outer wall of the allantois is adjacent to the egg shell and contains capillaries through which gas exchange occurs.

Caring for the offspring of reptiles is rare; it consists mainly of protecting the masonry.